/* Filename: ab.c
 * Description: 4.系统IO和标准IO比较实例
 *   strace ./ab
 * Last modified: humble 20200119 10:41
 */
#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>

static void usage(void);

int main(int argc, char **argv) {
    putchar('a');
    write(1,"b",1);
    putchar('a');
    write(1,"b",1);
    putchar('a');
    write(1,"b",1);
    //打印bbbaaa，putchar是标准IO(行缓冲)，最后退出才刷新三个a
    return 0;
}

static void usage(void) {
#define USAGE "Usage:\n\
  Helloworld\n"
    printf(USAGE);
}
